In the chemical and petrochemical industries it is often the case that mixtures of liquids and vapors have to be introduced into a treating zone, e.g. an inlet treating zone of a vertical column having adjacent treating zones in which gas and liquid are counter currently contacted to exchange heat or matter. An example of such a column is a fractionation column, e.g. a vacuum distillation column and compact gas-liquid separators as described in EP-A-195 464.
In such a column, during normal operation, liquid flows downwards from top to bottom, whereas gas flows upwards from bottom to top. In the distillation process, a fluid comprising a mixture of liquid and gas is inwardly and radially fed into a generally vertically disposed cylindrical distillation column at an inlet zone between the top and the bottom of the column. In installations having a large capacity and throughput, the supply velocity of the mixture is generally very high; these high supply velocities may be disadvantageous to the distribution of the fluid to be treated over the cross-section of the column into which it is fed.
It is in fact desirable, particularly in the distillation process, for the gas phase and the liquid phase to be separated as much as possible immediately after entering the column in the inlet treating zone and for each phase to be separately fed to adjacent treating zones, e.g. by passing through a tray, while being distributed over the column cross section as well as possible.
If no special measures are taken, it will not be possible to effect a proper separation of a gas/liquid mixture fed into the column at a high supply velocity, since the feed will then strike the wall situated opposite the inlet with excessive force, so that the gas subsequently rising up in the column entrains a large portion of the liquid phase. In addition, the liquid which has not been entrained flows for the most part downwards near the column wall opposite to the inlet, thereby causing an uneven distribution of the liquid over the adjacent tray below the inlet. Furthermore, the wall portion of the column opposite the feed may rapidly wear due to the strong impact of the liquid/vapor mixture, so that measures have to be taken to protect or to reinforce the column wall.
To alleviate the above problem, it has been proposed in GB 1 119 699 to provide a fluid inlet device for introducing a mixture of liquid and gas into the column, comprising a box-like arrangement comprising a series of vanes, placed one behind the other along a horizontally disposed central axis extending in radial inward direction of column. In this arrangement, the vanes deflect the mixture sideways relative to the central axis of the inlet device, such that the change in direction of the flow causes a first separation between gas and liquid due to inertia. After insertion into the treating zone, the gas flows upwards in the column, where further contacting with liquid supplied to the top of the column takes place. The separated liquid falls downwards from the vanes onto a gas/liquid contact tray below the inlet device.
Although the known fluid inlet device provides for a great improvement, the fluid inlet device causes a swirling flow of gas in the inlet treating zone. Such a swirling flow decreases the maximum feed rate and increases the height of the column needed to effect full distillation.
It would be advantageous to provide an improved device for treating a fluid having a fluid inlet for introducing a mixture of liquid and gas into the treating zone in which the swirling of the flow in the inlet treating zone is greatly reduced.